Insulation of a self-cooling beverage package

ABSTRACT

A self-cooling beverage package having a first cavity ( 10 ) containing a beverage for consumption, a second cavity ( 20 ) forming a heat exchanger and containing a refrigerant liquid and its vapor, a third cavity ( 30 ) containing means of pumping by adsorption of said vapor and means ( 50 ) of putting said second cavity into communication with said third cavity, characterised in that the third cavity ( 30 ) has an external thermal insulation layer ( 35 ).

The present invention relates to a beverage package device allowingcooling of its contents by sorption cooling method. The principle ofsuch a cooling method consists of evaporating a liquid under the effectof a partial vacuum maintained by pumping the vapours of said liquid.The invention is applicable most particularly to the cooling of abeverage contained in a can or bottle type closed package.

The object of the present invention is thus to allow the consumption ofa beverage at an ideal temperature anywhere and at any time.

The implementation of the method of sorption cooling is known and hasbeen the subject of much research in the prior art. Many devices havebeen proposed, associating a heat exchanger containing a refrigerantliquid to be evaporated with a cavity containing an adsorbent, inparticular for applications to self-cooling beverage packages.

One of the difficulties of implementing such a method of sorptioncooling consists of managing the heat deposited in the adsorbent duringthe adsorption reaction. This is because, when the adsorbent, generallya desiccant such as zeolites, adsorbs the vapor of the refrigerantliquid, it heats up and therefore loses most of its adsorption capacity.Removing part of this heat deposited in the dessicant improvessignificantly the cooling performances of the device.

Various solutions for limiting the rise in temperature of the adsorbenthave already been proposed in the prior art.

A first known solution, described in the patent U.S. Pat. No. 4,759,191,consists of removing the heat deposited in the adsorbent (a desiccant)by means of a heat sink consisting of a material in thermal contact withthe desiccant, said material having either a solid-to-liquid phasechange, or a high heat capacity, or an endothermic reaction. The patentU.S. Pat. No. 4,949,549, from the same inventors, specifies the solutionadopted, namely a material with a phase change such as sodium acetate,the solid-to-liquid phase change of which is situated at 58° C. Thissolution nevertheless requires the implementation of a particularcontainer for the associated phase change material in the desiccantcontainer, which complicates the method of manufacture of suchself-cooling beverage packages because it requires efficient thermalcoupling between the dessicant and the heat sink material.

An adaptation of this solution, described in the patent U.S. Pat. No.5,048,301, consists of thermally insulating the adsorbent with the heatsink in an evacuated chamber inside the beverage can. Nevertheless, thissolution is complex to implement.

Patent application WO 01/10738 also describes a self cooling can using asorption cooling method with a heat sink material. Since the phasechange of the heat sink material occurs around 60° C., the dessicant andthe heat sink material are packaged in an insulating container toprotect the consumer from the hot material.

Another known solution, described in the patent U.S. Pat. No. 4,928,495,proposes storage of the heat deposited in the adsorbent (a desiccant) inwater, the heat capacity of which is relatively high. An alternative,described in the same patent, consists of wetting the external surfaceof the desiccant container in order to remove the calories byevaporation of this water wetting the desiccant container. Nevertheless,the implementation of such a device is complex and protection againstburns is no longer provided once the water wetting the external surfaceof the container has totally evaporated.

Another solution, described in the patent application FR 2 811 412,consists of disposing thermal insulation at the periphery of a block ofdesiccant, inside the container containing said desiccant. Thisinsulation is constituted by zeolites impregnated with resin in order toobstruct their porosity and prevent them adsorbing the vapours of therefrigerant liquid. By preventing the zeolites fulfilling theiradsorption function, their heating up is prevented.

The objective of the present invention is to propose an alternativesolution to managing the heat deposited in the adsorbent duringimplementation of the sorption cooling method as described previously.

The simplest solution would be to let the adsorbent heats up to itsequilibrium temperature and to provide enough adsorbent to achieve theproper cooling performance. The adsorbent for pumping the refrigerantliquid vapor advantageously consists of a dessicant such as a zeolite13× for example. During the adsorption of water vapor by such a zeolite,the adsorbent can reach 200° C. for an adsorption capacity of around 5%by mass of adsorbed water with respect to the mass of the desiccant.Thus, around 200 g of zeolite are sufficient to adsorb 10 g of water,the evaporation of which makes it possible to cool 330 ml of beverage by15° C. It is therefore not essential to remove the heat deposited in thedesiccant since the adsorption capacity limit is not reached.

With such a solution, the major difficulty is to provide the properinsulation for the heated adsorbent (about 200° C. for zeolites). Twoproblems must be considered:

-   -   avoid heating of the cooled beverage by heat flowing back from        the adsorbent to the evaporator and beverage can;    -   avoid excessive external temperature of the adsorbent container        for consumer safety and comfort.

To this end, the present invention proposes an insulation layer designdisposed around the adsorbent container which compels these twoproblems.

More particularly, the invention relates to a self-cooling beveragepackage device having a first cavity containing a beverage forconsumption, a second cavity forming a heat exchanger and containing arefrigerant liquid and its vapor, a third cavity containing adsorbentfor pumping of said vapor and means of putting said second cavity intocommunication with said third cavity for operation of the device,characterised in that the third cavity has an external thermalinsulation layer designed such that the heat flow from the adsorbentthrough the outside wall of the third cavity is larger or equal to theheat flow from the adsorbent to the second and first cavities duringoperation of the device.

According to one embodiment, the temperature of the external surface ofthe insulating layer rises to more then 70° C. during operation of thedevice.

According to one characteristic, the thermal insulation layer has athermal conductivity less than or equal to 500 W.m⁻².K⁻¹, andpreferentially between 20 and 60 W.m⁻².K⁻¹.

According to another embodiment, the thermal insulation layer includes amaterial melting at a temperature between 40° C. and 80° C. Possibly,the thermal insulation layer consists of at least two layers, one ofthem including the melting material.

According to embodiment, the thermal insulation layer surrounds thethird cavity consisting of a metal container or the thermal insulationlayer is constituted by the walls of a container forming the thirdcavity.

According to one embodiment, the thermal insulation layer extends aroundthe first cavity.

According to one embodiment, the thermal insulation layer has athermochromic label.

The features and advantages of the present invention will emerge in thecourse of the following description given by way of an illustrative andnon-limitation example, and produced with reference to the accompanyingfigures in which:

FIG. 1 is depicting a self-cooling beverage package according to theinvention,

FIG. 2 is depicting the insulation layer according to one embodiment ofthe invention,

FIG. 3 is depicting the insulation layer according to another embodimentof the invention.

Referring to FIG. 1, the self-cooling beverage package according to theinvention has a first cavity 10 containing a beverage for consumption, asecond cavity 20 forming a heat exchanger and containing a refrigerantliquid, such as water, and its vapor and a third cavity 30 containingdessicant 31 for pumping by adsorption of said vapor. The second cavity20 is also referred to as the evaporator and the third cavity 30 is alsoreferred to as the desiccant container. Means 50 of putting said secondcavity 20 into communication with said third cavity 30 are also providedfor operation of the sorption cooling method.

The third cavity 30 consists of a container guaranteeing good vacuumsealing necessary for correct operation of the pumping means. Generally,this container is metallic. The risk of burning therefrom is all thehigher. Thus, according to the invention, the third cavity 30 has athermal insulation layer 35.

According to the present invention, the first previously identifiedproblem (avoid heating of the cooled beverage by heat flowing back fromthe adsorbent container to the evaporator) is solved by an active heatshield concept which mainly works as follow:

As heat leaks out of the adsorbent 31, it cools down and consequently iscapable of adsorbing more refrigerant vapor, resulting in additionalcooling in the evaporator 20. In case of zeolites used as adsorbent,this additional cooling is about or above 50% of the heat leakage out ofthe adsorbent. The insulation layer 35 surrounding the dessicantcontainer 30 is designed such that the heat flow from the adsorbentthrough the outside wall of the third cavity is at least as large as theheat flow towards the evaporator and the beverage can (respectivelysecond 20 and first 10 cavities). With such insulation, the net effectis additional cooling of the beverage and not heating by dessicant heat.

Moreover, the second previously identified problem (avoid excessiveexternal temperature of the adsorbent container for customer safety andcomfort) is also solved by the insulation layer according to theinvention.

According to one preferred solution, the thermal insulation layer 35 isprovided with a conductivity adjusted to achieve an outer surface ofsaid insulation layer to reach 70° C. and up to 90° C. during thesorption cooling process. This relatively high external surfacetemperature allows extracting about 0.1 W.cm⁻² through naturalconvection. However, this external surface temperature falls down toabout 40-45° C. on contact with fingers. This temperature drop oncontact with a consumer fingers is due to the higher heat extraction byfingers as compared to the natural air convection (about three timesmore) combined with the high thermal gradient across the insulationlayer which ranges from 20° C. to 50° C.

This natural convection increases the absorption capacity of thedesiccant and advantageously contributes towards prolonging the beveragecooling process. The heat power extracted, of the order of a few watts,is not a determining factor for the initial cooling of the beveragewhich is typically 15° C. in 3 minutes, but it provides additionalcooling over a much longer period, typically 2° C. in 30 minutes, inorder to keep the beverage cool during its consumption.

The thermal conductivity of the insulation layer that achieves theseconditions is less then 100 W.m⁻².K⁻¹ and preferably ranges from 20 to60 W.m⁻².K⁻¹.

The temperature distribution (from inside the desiccant material 31, atthe adsorbent container wall 30, to outside the external insulation 35)can also be influenced by the heat coupling between the desiccant 31 andthe container wall 30 by providing an additional insulation inside thecontainer.

Such internal insulation can be achieved by a method described inpreviously cited patent application FR 2 811 412, or by an adequategeometrical structuring of the desiccant 31 close to the wall of thecontainer 30, such as ripples 39 as illustrated FIG. 2.

In this embodiment, the desiccant container wall 30 equilibriumtemperature is lowered and the required conductivity of the externalinsulation layer 35 must be higher to achieve the needed heat flow tothe outside atmosphere. In this configuration, the conductivity of theexternal insulation layer 35 ranges from 100 to 500 W.m⁻².K⁻¹. Since thedesiccant container walls temperature is lowered, the heat flow towardsthe beverage can and the evaporator (first 10 and second 20 cavities) isreduced.

According to an alternative solution, an illustration of which is givenFIG. 3, the insulation layer 35 includes a material melting at atemperature between 40° C. and 80° C. This phase change materialprovides an active heat shield between the dessicant container 30 andthe outside atmosphere such that the energy transmitted to the outsideatmosphere is less than the energy flowing out of the dessicantcontainer. The difference of energy corresponds essentially to thelatent heat of the melting material. According to this embodiment, theinsulation layer 35 consists of at least two layers 36, 37, one of them36 including the melting material. A typical material that can beincorporated in the insulation layer 36 is Sodium Acetate trihydratemelting at 58° C. An additional layer 37 of insulation without meltingmaterial is required to act as an thermal protection. This additionallayer 37 has a thermal conductivity less than 100 W.m⁻².K⁻¹, typically50. The phase change material can be incorporated in voids of theinsulation layer 36.

The thermal insulation layer 35 is surrounding the metallic third cavity30 and can be constituted by a layer of cardboard and/or a number oflayers of superposed paper and/or a plastic. It can be glued on theexternal surface of the third cavity 30 or be held by a heat-shrinkplastic tube. It typically has a thickness between 0.5 and 1.5 mm in thefirst described embodiment and can reach 3 to 5 or even 10 mm in theembodiment including melting material. The thermal insulation layer isadvantageously put in place after the filling of the beverage, inparticular in the case of pasteurised beverages where it is put in placeafter pasteurisation.

The heat leakage through the can wall of the beverage can (first cavity10) produces a thermal gradient along the adsorbent container wall 30.To optimise the heat leakage to the outside atmosphere while keepingadequate protection for the consumer, the insulation layer 35 thicknesscan be reduced as it gets closer to the boundary between the beveragecan 10 and the adsorbent container 30.

According to one particular embodiment, the thermal insulation layer 35can extend from the third cavity 30 containing the desiccant to thefirst cavity 10 containing the beverage for consumption. It can thuscontribute towards keeping the beverage cool during its consumption.

According to one embodiment, the thermal insulation layer 35 has athermochromic label 36, for example by printing of thermochromic inkdirectly on said insulating layer. This printing can be implementedopposite the desiccant container 30, for example on the hottest part ofthe self-cooling package. The appearance of the thermochromic ink at agiven temperature threshold, for example at 60° C., can constitute anindicator of correct operation of the self-cooling device.

It can also be envisaged disposing the thermochromic label opposite thecavity 10 containing the beverage for consumption and which will beactivated below a certain threshold, for example 10° C., in order toconstitute an indicator for ideal consumption of the beverage.

One possible alternative consists of implementing the thermal insulationlayer 35 directly by the walls of a container forming the third cavity30.

The present invention provides self-cooling beverage packages with aneffective physiological protection against the risks of burning due tothe rise in temperature of the adsorbent. In order to achieve anequivalent protection situated inside the metal adsorbent container,thermal insulation would have to have a thermal resistance five timesgreater, requiring more volume in the device and more material.

The thermal insulation layer according to the invention allows the useof an efficient adsorbent such as a zeolite without requiring recourseto heat sink which considerably complicate the manufacture of thedevice.

Moreover, the thermal insulation layer according to the invention makesit possible to naturally continue the cooling process and thus providesan addition to the initial rapid cooling in order to keep the beveragecool during its consumption.

1. A self-cooling package device having: a first cavity containing aproduct for consumption, a second cavity forming a heat exchanger andcontaining a refrigerant liquid and its vapor, a third cavity having anoutside wall and containing adsorbent for pumping of said vapor, andmeans for putting said second cavity into communication with said thirdcavity for operation of the device, wherein the third cavity is providedwith an external thermal insulation layer providing a physiologicalprotection against burns and designed such that the heat flow from theadsorbent through the outside wall of the third cavity and through theexternal insulation layer is larger or equal to the heat flow from theadsorbent towards the second and first cavities during operation of thedevice.
 2. A self-cooling package according to claim 1, wherein thetemperature of the external surface of the insulation layer rises tomore than 70° C. during operation of the device.
 3. A self-coolingpackage according to claim 1, wherein the thermal insulation layer has athermal conductance less than or equal to 500 W.m².K⁻¹.
 4. Aself-cooling package according to claim 3, wherein the thermalconductance of the insulating layer is between 20 and 60 W.m².K⁻¹.
 5. Aself-cooling package according claim 1, wherein the thermal insulationlayer has a thickness between 0.5 and 1.5 mm.
 6. A self-cooling packageaccording to claim 1, wherein the thermal insulation layer has avariable thickness.
 7. A self-cooling package according to claim 1,wherein the thermal insulation layer includes a material melting at atemperature between 40° C. and 80° C.
 8. A self-cooling packageaccording to claim 7, wherein the thermal insulation layer comprises atleast two layers, one of them including the melting material.
 9. Aself-cooling package according to claim 7, wherein the thermalinsulation layer has a thickness between 3 and 10 mm.
 10. A self-coolingpackage according to claim 1, wherein the thermal insulation layersurrounds the third cavity consisting of a metal container.
 11. Aself-cooling package according to claim 1, wherein the thermalinsulation layer extends around the first cavity.
 12. A self-coolingpackage according to claim 1, wherein the thermal insulation layer has athermochromic label.
 13. A self-cooling package according to claim 12,wherein the thermochromic label is disposed opposite the third cavity.14. A self-cooling package according to claim 12, wherein thethermochromic label is disposed opposite the first cavity.
 15. Aself-cooling package according to claim 1, wherein the thermalinsulation layer comprises cardboard and/or paper and/or plastic.
 16. Amethod for cooling the content of a package, comprising the steps of:providing a package having a first cavity containing a product to berefrigerated, a second cavity forming a head exchanger and containing arefrigerant liquid and its vapor, and a third cavity having an outsidewall and containing adsorbent, said third cavity being provided with anexternal thermal insulation layer; putting into communication said thirdcavity with said second cavity; cooling down the product within saidfirst cavity by pumping vapor of said refrigerant liquid by saidadsorbent; avoiding heating back of cooled product within said firstcavity by allowing the heat flow from the adsorbent through the outsidewall of the third cavity and through the external thermal insulationlayer to be larger or equal to the heat flow from the adsorbent towardsthe second and first cavities; and avoiding excessive externaltemperature of the third cavity containing the adsorbent by allowing athermal gradient across the insulation layer ranging from 20° C. to 50°C.